Aluminum or aluminum alloy sputtering target and method for manufacturing the same

ABSTRACT

The sputtering target is manufactured by adjusting the ratio of the gas flow volume (Nm 3 )/molten liquid flow mass (kg) to 5 Nm 3 /kg or more in the gas atomizing step of the spray forming method using an Al or Al alloy sputtering target material in which the maximum length of all the inclusions is 20 μm or less.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a sputtering target materialcomprising aluminum or an aluminum alloy (referred to an aluminum oraluminum alloy sputtering target hereinafter), and a method formanufacturing the same. The present invention especially relates to analuminum or aluminum alloy sputtering target material for use in formingsemiconductor electrode films and a method for manufacturing the same,relating among all to an aluminum or aluminum alloy sputtering targetfor forming semiconductor electrode films being advantageous as liquidcrystal display electrodes (thin film wiring and the electrode itself)and a method for manufacturing the same.

[0003] 2. Description of the Related Art

[0004] Use of liquid crystal displays (abbreviated as LCD hereinafter)has been recently expanded since it can be made thin and lightweightbesides consuming small amount of electric power while maintaining highresolution as compared with conventional cathode-ray tubes (CRT). TheLCDs having a structure in which semiconductor devices such as thin filmtransistors (abbreviated as TFT hereinafter) are integrated as switchingelements have been recently proposed and widely used in order to enhanceimage quality. The TFT as used herein refers to an active elementproduced by connecting semiconductor electrodes comprising a thin metalfilm to a semiconductor film formed on an insulation substrate made of,for example, a glass. The semiconductor electrode is defined as anelectrode to be used as a part of the TFT including a thin film wiringand the electrode itself. Once the active element is formed into theTFT, the wiring and the electrode itself are put into electricalcontinuity with each other.

[0005] Among various characteristics required for the LCD as describedabove, making electrical resistivity small for preventing signal delayis being one of the most crucial characteristics in compliance with thetrends toward large size or highly sophisticated LCDs.

[0006] The semiconductor electrode for use in the LCD is produced by asputtering method in which a sputtering target is used for sputtering.The sputtering target serves as a sputtering source for forming thesemiconductor electrode on a substrate by sputtering, usually comprisinga circular or rectangular plate. Atoms constituting the sputteringtarget are emitted into the space and deposited on the confrontingsubstrate by exchange of kinetic momentum when accelerated particlescollide with the surface of the sputtering target during sputtering.

[0007] High melting point metals such as Ta, Mo, Cr, Ti, W, Zr and Nbhave been used for sputtering target materials for forming thesesemiconductor electrodes for use in the LCD. However, since the highmelting point metals such as Ta, Mo, Cr, Ti, W, Zr and Nb have so highspecific resistivity when they are formed into thin films that theirapplication for the foregoing object have became difficult, becausecurrently used LSIs are so highly integrated that a wiring width of asfine as 1 μm is required for the circuit. In other words, resistivity ofthe semiconductor electrode manufactured by using the sputtering targetmaterial comprising the foregoing high melting point metals is so highthat the material became hardly compatible with fine wiring width asdescribed above. Accordingly, development of semiconductor electrodematerials having low resistivity as substitutes of the foregoing highmelting point metals is desired.

[0008] Examples of the semiconductor electrode materials with desirablelow resistivity include Au, Cu and Al. However, Au does not exhibitsuitable etching characteristic, besides it is expensive, required forforming into a desired pattern after depositing a sheet of electrode, oran electrode film (a wiring film). Cu has some problems in adhesiveproperty and corrosion resistance while Al has so poor heat resistancethat minute hills called hillocks appear on the surface during theheating step (at about 250 to 400° C.), an inevitable production processof the TFT, after forming the electrode film. Because the electrode filmis formed at the lowermost layer in the TFT-LCD, other films can not belaminated thereon when these hillocks are generated.

[0009] An electrode film comprising an Al alloy containing the alloycomponents as disclosed in Japanese Unexamined Patent Publication No.7-45555 which is hereby fully incorporated by reference, and an Al alloysputtering target for forming such Al alloy electrode film are proposedas a means for avoiding the hillock problems in the Al electrode film.

[0010] However, there arise another problems that particles and splashesare appeared to generate when the semiconductor electrode is formed onthe substrate by sputtering using the sputtering target materialscomprising the Al or Al alloys as described above. Particles scatteringfrom the target are turned into clusters that directly adhere to thethin film on the substrate, or adhered or deposited layers on thesurrounding wall or components is peeled off to adhere to the thin filmon the substrate (so-called particle problem). Otherwise, droplets ofthe target material are scattered and adhere to the thin film on thesubstrate (so-called splash problem).

[0011] While the problems of particle and splash generation has beensolved by decreasing the content of inclusion in the sputtering targetmaterials as small as possible, it was pointed out in JapaneseUnexamined Patent Publication No. 9-25564 which is hereby fullyincorporated by reference that the utmost number of the inclusionshaving a mean particle size of 10 μm or more in the target should bereduced to less than 40 particles/cm². However, the countermeasure asdescribed above was proved to be insufficient for solving the problemsof particle and splash generation.

[0012] Among the problems of particle and splash generation, the crucialproblem that is urgently to be solved is that generation of splashprovides serious obstacle on the performance of the thin film on thesubstrate or of the semiconductor electrode formed thereon. Splashestend to be formed especially when an Al alloy sputtering target is usedin order to prevent hillocks from appearing on the Al electrode film.

[0013] Splashes are generated not only in forming the foregoingsemiconductor electrode for use in LCDs, but also in forming wiring ofsemiconductor integrated circuits and reflection layers of magneticrecording and photomagnetic recording media by sputtering as well.

SUMMARY OF THE INVENTION

[0014] Accordingly, the object of the present invention is to provide analuminum or aluminum alloy sputtering target material hardly generatingsplashes when used for sputtering, and a method for manufacturing thesame.

[0015] In a first aspect, the present invention provides an aluminum oraluminum alloy sputtering target comprising aluminum or an aluminumalloy containing inclusions having a maximum length of 20 μm or less.

[0016] The sputtering target material as described above allows splashesto be suppressed from generating during sputtering. The maximum lengthof the inclusions is limited to 20 μm or less because the inclusionswith a maximum length of more than 20 μm makes the splashes to bereadily generated owing to these inclusions, insufficiently suppressinggeneration of the splashes.

[0017] It is advantageous that all the inclusions have a maximum lengthof 10 μm or less.

[0018] The sputtering target material with the maximum length of theinclusions as described above allows the splashes to be hardlygenerated, more securely suppressing splash generation.

[0019] In a preferred embodiment, the present invention provides amethod for fabricating an Al or Al alloy sputtering target material by aspray forming method, wherein the ratio of the gas flow volume(Nm³)/molten liquid flow mass (kg) in a gas atomizing step of the sprayforming method is adjusted to 5 Nm³/kg or more.

[0020] In the method described above, the molten liquid of the Al or Alalloy is atomized to be dispersed into molten or semi-molten smallparticles as well as crashing the inclusion into small pieces in theatomizing step of the spray forming method. These small particles ofsemi-molten Al or Al alloy are successively deposited by spraying onto abottom floor or in a mold, thereby forming the Al or Al alloy sputteringtarget material. When the ratio of the gas flow volume (Nm³)/moltenliquid flow mass (kg) in the gas atomizing step of the spray formingmethod is adjusted to 5 Nm³/kg or more, the size (the maximum length) ofall the inclusions after crushing becomes 20 μm or less, making itpossible to obtain the Al or Al alloy sputtering target material inwhich the size of all the inclusions is 20 μm or less.

[0021] It is also advantageous to adjust the ratio of the gas flowvolume (Nm³)/molten liquid flow mass (kg) to 10 Nm³/kg or more.

[0022] When the ratio of the gas flow volume (Nm³)/molten liquid flowmass (kg) is adjusted to 10 Nm³/kg or more, an Al or Al alloy sputteringtarget material in which the size (the maximum length) of all theinclusions is 10 μm or less.

[0023] It is also advantageous to use nitrogen gas for the atomizing gasin the gas atomizing step along with adjusting the ratio of the gas flowvolume (Nm³)/molten liquid flow mass (kg) to 10 Nm³/kg or more.

[0024] The Al or Al alloy sputtering target material in which the size(the maximum length) of all the inclusions is 10 μm or less, along withcontaining 0.1 mass % or less of nitrogen, can be obtained to allowsplashes to be hardly generated during sputtering, thereby enabling toform an Al or Al alloy thin film with small specific resistivity.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025]FIG. 1 denotes a table indicating the sputtering conditionsdescribed in the Examples;

[0026]FIG. 2 denotes a table indicating the manufacturing conditions ofthe sputtering target material according to Examples 1 to 4, and theresults of investigations on the size of the inclusion, the number ofthe splash having a size of 10 μm or more, and the oxygen content;

[0027]FIG. 3 denotes a table indicating the manufacturing conditions ofthe sputtering target according to Examples 5 to 9, and the results ofinvestigations on the size of the inclusion, the number of the splashhaving a size of 10 μm or more, and the oxygen content;

[0028]FIG. 4 denotes a table indicating the sputtering conditions of thesputtering target material according to Example 10;

[0029]FIG. 5 denotes a table showing the relation between the maximumlength of the inclusion and the number of the splash having a size of 10μm or more with respect to the Al or Al alloy sputtering target materialaccording to Example 4;

[0030]FIG. 6 denotes a graph showing the relation between the maximumlength of the inclusion and the number of the splash having a size of 10μm or more with respect to the Al or Al alloy sputtering target materialaccording to Example 4; and

[0031]FIG. 7 denotes a graph showing the relation between the nitrogencontent and electrical resistivity of the thin film obtained withrespect to the sputtering target material according to Example 10.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0032] The Al or Al alloy sputtering target material according to thepreferred embodiment of the present invention and the method forfabricating the same will be described hereinafter.

[0033] The present invention was completed based on the results obtainedthrough intensive studies for developing the Al or Al alloy sputteringtarget material that hardly generates splashes.

[0034] The inventors of the present invention have manufactured the Alsputtering target material and Al alloy sputtering target materialhaving various size of inclusion. The behavior of these sputteringtarget materials during sputtering has been fully investigated usingthese materials as sputtering targets.

[0035] The results indicated that the splash is generated when coolingof the target material is partially inhibited around the inclusion,especially at just above the inclusion, in the sputtering targetmaterial. In other words, it was found that the site around theinclusion is melted by plasma heating during sputtering and the splashis generated by allowing the molten layer to scatter by electromagneticforce forming droplets, that the splash is largely correlated with thesize of the inclusion rather than the amount of the inclusion asdescribed in Japanese Unexamined Patent Publication No. 9-25564, andthat generation of the splash can be suppressed when the size (themaximum length, or the length of the portion having the maximum length)of the inclusion is 20 μm or less, or little splashes are generated whenthe size of the inclusion is 10 μm or less.

[0036] The size of the portion where cooling is inhibited by theinclusion during sputtering becomes small in the Al sputtering targetmaterial and Al alloy sputtering target material having the inclusionwith a size (the maximum length) of 20 μm or less and the molten layeris hardly formed. Accordingly, the scattering frequency of the moltenlayer as droplets, or the frequency of splash generation, is so markedlydecreased to sufficiently suppress generation of the splash. Especially,when the size of all the inclusion is 10 μm or less, the splash issubstantially not generated.

[0037] In the first step of the method for manufacturing the Al or Alalloy sputtering target material according to the present invention, aingot is produced by a spray forming method using a molten liquid. Themolten liquid of Al or an Al alloy is deposited by gas atomizing toobtain a ingot. The ratio of the gas flow volume (Nm³)/molten liquidflow mass (kg) in the gas atomizing step of the spray forming method isadjusted to 5 Nm³/kg or more, thereby enabling to obtain the Al or Alalloy sputtering target material according to the present embodiment, orthe sputtering target material comprising the Al or Al alloy having themaximum length of all the inclusions of 20 μm or less. The ratio of thegas flow volume (Nm³)/molten liquid flow mass (kg) in the gas atomizingstep of the spray forming method is adjusted to 5 Nm³/kg or morebecause, when the ratio is less than 5 Nm³/kg, a substantial number ofinclusions having the maximum length of more than 20 μm are included inthe Al or Al alloy sputtering target material, the inclusion serving astrigger points for generating the splashes during sputtering in thesputtering target material as described above.

[0038] The Al or Al alloy sputtering target material obtained by thespray forming method as described above contains a higher concentrationof oxygen in the material than the Al or Al alloy sputtering targetmaterial obtained by the vacuum melting method. However, the splashesare hardly generated in the former material as compared with the lattermaterial during sputtering, in spite of the fact that the formercontains larger amount of the inclusions in the material than thelatter. This is because the former contains smaller size of inclusionsthan the latter. In other words, the large number of the inclusions havelittle influence when the size of the inclusion is small as in theformer case, hardly generating the splashes. In the melting methods invacuum or in the air, so many inclusions having a size of more than 20μm are formed that they serve as trigger points of splash generation.

[0039] Nitrogen concentration in the Al or Al alloy sputtering targetmaterial becomes high when nitrogen gas is used for the atomizing gas inthe atomizing step of the spray forming method in manufacturing the Alor Al alloy sputtering target material by the spray forming method. TheAl or Al alloy thin film for the Al electrode, manufactured bysputtering using the sputtering target material containing a highconcentration of nitrogen as described above, naturally contains a highconcentration of nitrogen, showing high specific resistivity by beinginfluenced by included nitrogen. When the Al alloy thin film is formedusing a sputtering target material comprising an Al—Ti alloy (Al alloycontaining Ti) for example, electrical resistivity of the Al thin filmbecomes higher as the nitrogen concentration in the sputtering targetobtained is higher as shown in FIG. 7. Accordingly, a lower nitrogenconcentration in the Al or Al alloy sputtering target material ispreferable from the view point of specific resistivity of the Al or Alalloy sputtering target material, a content of 0.1 mass % or less beingdesirable.

[0040] The upper limit of the nitrogen concentration was set to 0.1 mass% or less because a material having resistivity comparable to that ofthe material containing 0% of nitrogen is urgently desired from the viewpoint of suppressing increase of specific resistivity due to increase ofthe nitrogen concentration.

[0041] Accordingly, the inventors of the present invention have carriedout intensive studies for developing the technology by which thenitrogen concentration of the Al or Al alloy sputtering target materialobtained can be reduced especially to 0.1 mass % or less when nitrogengas is used for the atomizing gas in the gas atomizing step of the sprayforming method. It was found from the results of the investigation that,when the ratio of the gas flow volume (Nm³)/molten liquid flow mass(kg), or the ratio of nitrogen gas flow volume Nm³)/molten liquid flowmass (kg), is adjusted to 10 Nm³/kg or more, an Al or Al alloysputtering target material containing 0.1 mass % or less of nitrogen canbe obtained.

[0042] The size (the maximum length) of all the inclusions is 10 μm orless in the Al or Al alloy sputtering target material obtained by themethod as hitherto described, hardly generating the splashes duringsputtering since the material was obtained by the manufacturing methodhaving basically the same construction as that of the manufacturingmethod according to the present invention.

[0043] Accordingly, the Al or Al alloy sputtering target material inwhich the size (the maximum length) of all the inclusions is 10 μm orless along with containing 0.1 mass % or less of nitrogen can beobtained when nitrogen gas is used for the atomizing gas in the gasatomizing step of the spray forming method for producing the Al or Alalloy sputtering target material, wherein the ratio of the gas flowvolume (Nm³)/molten liquid mass (kg) is adjusted to 10 Nm³/kg or more.The splashes are hardly generated during sputtering in the Al or Alalloy sputtering target material obtained by the method as describedabove, making it possible to form the Al or Al alloy thin film havinglow specific resistivity.

[0044] When the ratio of the gas flow volume (Nm³)/molten liquid flowmass (kg), or the nitrogen gas flow volume (Nm³)/molten liquid flow mass(kg), in the gas atomizing step is adjusted to 10 Nm³/kg or more, the Alor Al alloy sputtering target material containing 0.1 mass % or less ofnitrogen can be obtained by using nitrogen gas for the atomizing gas inthe gas atomizing step of the spray forming method as hithertodescribed. This is because, after allowing droplets (molten orsemi-molten small particles) to deposit on the bottom floor or in themold, the droplets are quickly solidified by nitrogen gas, hardlyinducing a reaction between Al and N to reduce the amount of nitrideformed.

[0045] When the ratio of the nitrogen gas flow volume (Nm³)/moltenliquid flow mass (kg) described above is less than 10 Nm³/kg, cooling ofthe droplets deposited on the bottom floor or in the mold, especially atthe center of the deposit (deposited layer of the droplets) becomesinsufficient, making the reaction of Al with N relatively easy to form alot of nitride by the reaction, thereby increasing the nitrogenconcentration in the Al or Al alloy sputtering target material obtainedto more than 0.1 mass %.

[0046] The maximum length of the inclusion refers to the length of thelargest part in the inclusion in the present invention. For example, themaximum length corresponds to the diameter when the inclusion assumes aspherical shape or to the maximum side length when the inclusion assumesa nearly rectangular shape. The term that the maximum length of all theinclusions is 20 μm or less means that all the inclusions in thematerial have a maximum length of 20 μm or less.

[0047] The flow mass of the molten liquid in the gas atomizing step ofthe spray forming method refers to a mass of the molten liquid per unittime flowing out of the molten liquid exit of the vessel containing themolten liquid. The gas flow volume in the step refers to the volume perunit time flowing out of the gas exit of the atomizing gas source forgas atomizing the flowing molten liquid.

[0048] The ratio of the gas flow volume (Nm³)/molten liquid flow mass(kg) in the gas atomizing step of the spray foing method refers to theratio between the gas flow volume and molten liquid flow mass when themolten liquid flow mass is expressed by kg/unit time and the gas flowvolume is expressed by Nm³/unit time, or the ratio of the gas flowvolume (Nm³/unit time)/molten liquid flow mass (kg/unit time). Thedefinition of the unit time should be the same in the expression of themolten liquid flow mass and gas flow volume. The gas flow volume(Nm³)/molten liquid flow mass (kg) described above is also referred tothe gas/metal ratio.

[0049] For example, when the gas flow volume is 40 Nm³/min and themolten liquid flow mass is 4 kg/min, the ratio of the gas flow volume(Nm³)/molten liquid flow mass (kg) is expressed by 40 (Nm³/min)/4(kg/min) or 40 (Nm³)/4 (kg), or 10 Nm³/min.

EXAMPLES Example 1 to 3

[0050] An Al—Nd alloy containing 2 at % (atomic percentage) of Nd (Al—Nd(2 at %) alloy) was melted and a ingot was made using the alloy by thespray forming method. The molten liquid of the Al—Nd (2 at %) alloy wassubjected to gas atomization to deposit in the mold, thereby obtaining aingot of the Al—Nd (2 at %) alloy. Nitrogen gas was used as theatomizing gas in the gas atomizing step of the spray forming method. Theratios of the nitrogen gas flow volume (Nm³)/molten liquid mass (kg)were adjusted to 6 Nm³/kg, 10 Nm³/kg or 15 Nm³/kg, respectively, in thegas atomizing step of the spray forming method. The method for makingthe ingot of the Al—Nd (2 at %) alloy (the sputtering target material)described above corresponds to the production method in the presentembodiment.

[0051] After forging and rolling of the ingot, a disk of the sputteringtarget material of the Al—Nd (2 at %) alloy with a diameter of 4 incheswas manufactured by machining.

[0052] The size (the maximum diameter) of the inclusion and oxygencontent, as well as the frequency of generation of the splashes, wereinvestigated with respect to the sputtering target material of the Al—Nd(2 at %) alloy fabricated as described above.

[0053] Samples for microscopic measurement of the size of the inclusionswere taken from the sputtering target material and, after polishing thesamples, were observed under an optical microscope to measure the sizeof the inclusion. Oxygen content was determined by gas analysis of thesample taken from the sputtering target material.

[0054] For the purpose of investigating the frequency of splashgeneration, the sputtering target material was subjected to sputteringfor 1 hour under the sputtering conditions listed in FIG. 1. Afterforming a thin film of the Al—Nd (2 at %) alloy on the substrate, thesurface of this thin film was observed under an optical microscope tocount the number of the splashes having a size (the maximum length) of10 μm or more, since the splash having a size of 10 μm or more causes asevere problem on the performance of the thin film.

[0055] The results of measurements with respect to the size of theinclusion, oxygen content and the number of splashes having a size of 10μm or more are listed in FIG. 2.

[0056] It was shown in FIG. 2 that all the sizes of the inclusions were20 μm or less in Examples 1 to 3. The maximum length of the inclusion inthe Al—Nd (2 at %) sputtering target material, obtained by adjusting theratio of the nitrogen gas flow volume (Nm³)/molten liquid mass (kg) to 6Nm³/kg, was 16 μm, the maximum length of the inclusion in the Al—Nd (2at %) sputtering target material, obtained by adjusting the ratio of thenitrogen gas flow volume (Nm³)/molten liquid mass (kg) to 10 Nm³/kg, was8 μm, and the maximum length of the inclusion in the Al—Nd (2 at %)sputtering target material, obtained by adjusting the ratio of thenitrogen gas flow volume (Nm³)/molten liquid mass (kg) to 15 Nm³/kg, was4 μm. These Al—Nd (2 at %) sputtering target materials refer to thesputtering target material according to Example 1, the sputtering targetmaterial according to Example 2 and the sputtering target materialaccording to Example 3, respectively, in the order of the abovedescription hereinafter.

[0057] The numbers of splashes having a size (the maximum length) of 10μm or more were 10, 5 and 3 in the sputtering target materials accordingto Example 1, Example 2 and Example 3, respectively. The frequencies ofslush generation with a size of 10 μm or more that adversely affect theperformance of the thin film were very small in Examples 1 to 3. Whenthe number of the splashes having a size of 10 μm or more is adjusted to10 or less, a significant technical achievement that allows the problemof making the wiring width very fine to be solved would be attained.

Comparative Example 1

[0058] A disk shaped Al—Nd (2 at %) sputtering target material (referredto the sputtering target material according to Comparative Example 1hereinafter) with a diameter of 4 inches was manufactured by machiningafter melting the Al—Nd (2 at %) alloy in the air followed by castingand rolling.

[0059] The maximum length of the inclusion and other characteristics inthe sputtering target material according to Comparative Example 1 wereinvestigated by the same method as in Examples 1 to 3. The results arelisted in FIG. 2. It is evident from FIG. 2 that the maximum length ofthe inclusion in the sputtering target material according to ComparativeExample 1 was 60 μm, along with showing the number of the splashes witha size of 10 μm or more of as large as 54.

Comparative Example 2

[0060] A disk shaped Al—Nd (2 at %) sputtering target material (referredto the sputtering target material according to Comparative Example 2hereinafter) with a diameter of 4 inches was manufactured by machiningafter melting the Al—Nd (2 at %) alloy in vacuum followed by casting androlling.

[0061] The maximum length of the inclusion and other characteristics inthe sputtering target material according to Comparative Example 2 wereinvestigated by the same method as in Examples 1 to 3. The results arelisted in FIG. 2. It is evident from FIG. 2 that the maximum length ofthe inclusion in the sputtering target material according to ComparativeExample 2 was 30 μm, along with showing the number of the splashes witha size of 10 μm or more of as large as 25.

[0062] The results in Comparative examples 1 and 2 clearly shows thatthe size of all the inclusions can not be adjusted to 20 μm or less whenthe alloy is melted in the air or in vacuum.

Comparative Example 3

[0063] A disk shaped (4 inches in diameter) Al—Nd (2 at %) alloysputtering target material (referred to the sputtering target materialaccording to Comparative Example 3 hereinafter) was manufactured by thesame method in Examples 1 to 3, except that the ratio of the nitrogengas flow volume (Nm³)/molten liquid flow mass (kg) in the gas atomizingstep of the spray forming method was adjusted to 4 Nm³/kg as shown inFIG. 2.

[0064] The maximum length of the inclusion and other characteristics inthe sputtering target material according to Comparative Example 3 wereinvestigated by the same method as in Examples 1 to 3. The results arelisted in FIG. 2. It is evident from FIG. 2 that the maximum length ofthe inclusion in the sputtering target material according to ComparativeExample 3 was 25 μm, along with showing the number of the splashes witha size of 10 μm or more of as large as 20.

Example 4

[0065] An Al—Nd (2 at %) alloy sputtering target material wasmanufactured by the same method as in Examples 1 to 3. The ratio of thenitrogen gas flow volume (Nm³)/molten liquid flow mass (kg) in the gasatomizing step of the spray forming method was used as variableparameters in order to allow the maximum length of the inclusion in thesputtering target material to change.

[0066] The maximum length of the inclusion and the number of splasheshaving a size of 10 μm or more generated during sputtering in thesputtering target material described above were investigated by the samemethod as in Examples 1 to 3. The relation between the maximum length ofthe inclusion and the number of splashes with a size of 10 μm or more,obtained based on the investigations above, is shown in FIG. 6.

[0067] It can be seen from FIG. 6 that, while the number of splasheswith a size of 10 μm or more rapidly increases as the maximum length ofthe inclusion is increased in the region where the maximum length of theinclusion is more than 20 μm, little number of splashes with a size of10 μm or more are found in the region where the maximum length of theinclusion is 20 μm or less, indicating that splashes are hardlygenerated.

[0068] Although the results as hitherto described in Examples 1 to 4 andin Comparative Example 3 are obtained by using nitrogen gas as theatomizing gas in the gas atomizing step of the spray forming method, thesame results can be obtained when other atomizing gases such as argongas are used instead of nitrogen gas.

Examples 5 to 7

[0069] An Al—Ti alloy (Al alloy containing Ti) was melted to make aingot by the spray forming method. Nitrogen gas was used as theatomizing gas in the gas atomizing step of the spray forming method. Theratios of the nitrogen gas flow volume (Nm³)/molten liquid flow mass(kg) in this gas atomizing step were changed to 14.3 Nm³/kg, 12.9 Nm³/kgand 10.0 Nm³/kg as shown in FIG. 3.

[0070] The content of nitrogen (nitrogen concentration) in the ingotabove was measured by nitrogen gas analysis of the samples taken fromthe ingot for the nitrogen gas analysis sample. After forging androlling of the ingot, a disk of the sputtering target material of theAl—Ti alloy with a diameter of 4 inches was manufactured by machining.Next, a thin film of the Al—Ti alloy was formed on the substrate bysputtering under the sputtering condition shown in FIG. 4 using thesputtering target material described above. After a conventional heattreatment, the electric resistivity of this thin film was measured. Thethin film was processed by photolithography as a resistivity measuringpattern with a dimension of 100 μm in width and 10 μm in length andspecific resistivity was measured by a four point probe method. Theresults of measurements are shown in FIG. 3. The nitrogen contents wereas low as 0.015, 0.018 and 0.027 mass %, respectively, all being 0.1mass % or less, allowing the increase of the electrical resistivityascribed to respective nitrogen contents (0.1 mass % or less) to besuppressed below 0.11 μΩ.cm, 0.13 μΩ.cm and 0.20 μΩ.cm.

Examples 8 and 9

[0071] An Al—Ti alloy was melted to make an ingot by the spray formingmethod. Nitrogen gas was used as the atomizing gas in the gas atomizingstep of the spray forming method. The ratios of the nitrogen gas flowvolume (Nm³)/molten liquid flow mass (kg) in this gas atomizing stepwere changed to 14.3 Nm³/kg and 10.0 Nm³/kg as shown in FIG. 3.

[0072] The content of nitrogen in the ingot in Examples 8 and 9 wasmeasured by the same method as in Examples 5 to 7. The results ofmeasurements are shown in FIG. 3. The nitrogen contents were as low as0.012 and 0.020 mass %.

[0073] While a smaller nitrogen content is preferable for reducingelectrical resistivity, the nitrogen content will be discussed inReference examples 1 to 4 below.

Reference Examples 1 and 2

[0074] Al—Ti alloy ingot were made by the same method as in Examples 5to 7, except that the ratios of the nitrogen gas flow volume(Nm³)/molten liquid flow mass (kg) were adjusted to 8.88 and 8.93 Nm³/kgas shown in FIG. 3.

[0075] Nitrogen contents of the ingot in Reference Example 1 and 2 weremeasured by the same method as in Examples 5 to 7. The results of themeasurements are shown in FIG. 3. The nitrogen contents in respectivesamples are 0.13 and 0.41 mass %, all exceeding 0.1 mass %.

Reference Examples 3 and 4

[0076] Al—Ti alloy ingots were made by the same method as in Examples 8and 9, except that the ratios of the nitrogen gas flow volume(Nm³)/molten liquid flow mass (kg) were adjusted to 9.0 and 8.9 Nm³/kgas shown in FIG. 3.

[0077] Nitrogen contents of the ingots in Reference Example 3 and 4 weremeasured by the same method as in Examples 5 to 7. The results of themeasurements are shown in FIG. 3. The nitrogen contents in respectivesamples are 0.11 and 0.33 mass %, all exceeding 0.1 mass %.

Example 10

[0078] An Al alloy sputtering target material was manufactured by thesame method as in Examples 1 to 3 by using an Al—Ti alloy instead of theAl—Nd alloy as the Al alloy. The ratio of the nitrogen gas flow volume(Nm³)/molten liquid flow mass (kg) in the gas atomizing step of thespray forming method was used as variable parameters in order to allowthe nitrogen content in the sputtering target material to change.

[0079] A thin film of the Al—Ti alloy was formed on the substrate bysputtering under the sputtering condition shown in FIG. 4 using thesputtering target material described above. After a conventional heattreatment, the electric resistivity of this thin film was measured. Thethin film was processed by photolithography as a resistivity measuringpattern with a dimension of 100 μm in width and 10 μm in length andspecific resistivity was measured by a four point probe method.

[0080] The nitrogen content in the sputtering target material accordingto Example 10 was measured by the same method as in Examples 5 to 7.

[0081] The relation between the nitrogen content in the sputteringtarget material and electrical resistivity of the thin film obtained wasdetermined based on the results of measurements described above. Theresults are shown in FIG. 7. FIG. 7 shows that the electricalresistivity of the Al alloy thin film formed becomes smaller as thenitrogen content in the sputtering target material is lower.

[0082] While the results as hitherto described are obtained by using theAl—Nd alloy and Al—Ti alloy as the Al alloy in Examples 1 to 10,Comparative examples 1 to 3 and Reference Examples 1 to 4, the sametendency may be obtained using Al—Ta, Al—Fe, Al—Co, Al—Ni and Al—REM(rare earth metal) alloys instead of these Al alloys.

[0083] While the invention has been described in detail and withreference to specific embodiments thereof, it will be apparent to thoseskilled in the art that various changes and modifications can be madetherein without departing from the spirit and the scope thereof.

[0084] The entire disclosure of Japanese Patent Application No. 10-40520filed on Feb. 23, 1998 including specification, claims, drawings andsummary are incorporated herein by reference in its entirety.

What is claimed is:
 1. A method for manufacturing an aluminum oraluminum alloy sputtering target material comprising aluminum oraluminum alloy containing inclusions having a maximum length of 20 μm,wherein the ratio of the gas volume (Nm³)/the liquid mass (kg) is 5Nm³/kg or more in a spray forming method including the step of obtainingan aluminum or aluminum alloy ingot by a gas atomizing step of a moltenliquid having aluminum or aluminum alloy.
 2. A method for manufacturingan aluminum or aluminum alloy sputtering target material according toclaim 1 , wherein the ratio of the gas volume (Nm³)/the liquid mass (kg)is adjusted to be 10 Nm³/kg or more.
 3. A method for manufacturing analuminum or aluminum alloy sputtering target material according to claim2 , wherein nitrogen gas is used for atomizing gas in the gas atomizingstep.
 4. A method for manufacturing an aluminum or aluminum alloysputtering target material comprising aluminum or aluminum alloycontaining inclusions having a maximum length of 20 μm comprises:melting an material having aluminum or aluminum alloy ingot into aliquid flow; atomizing a gas flow; spraying the liquid flow onto asurface by means of said gas flow, wherein the ratio of the gas flowvolume (Nm³)/the liquid flow mass (kg) is 5 Nm³/kg or more; anddepositing on said surface an aluminum or aluminum alloy sputteringtarget material comprising aluminum or aluminum alloy containinginclusions having a maximum length of 20 μm.
 5. A method formanufacturing an aluminum or aluminum alloy sputtering target materialaccording to claim 4 , wherein the ratio of the gas flow volume(Nm³)/the liquid flow mass (kg) is adjusted to be 10 Nm³/kg or more. 6.A method for manufacturing an aluminum or aluminum alloy sputteringtarget material according to claim 5 , wherein nitrogen gas is used forthe gas flow.
 7. A method for manufacturing an aluminum or aluminumalloy sputtering target material comprising aluminum or aluminum alloycontaining inclusions having a maximum length of 10 μm comprises:melting an material having aluminum or aluminum alloy ingot into aliquid flow; atomizing a gas flow; spraying the liquid flow onto asurface by means of said gas flow, wherein the ratio of the gas flowvolume (Nm³)/the liquid flow mass (kg) is 5 Nm³/kg or more; anddepositing on said surface an aluminum or aluminum alloy sputteringtarget material comprising aluminum or aluminum alloy containinginclusions having a maximum length of 10 μm.
 8. A method formanufacturing an aluminum or aluminum alloy sputtering target materialaccording to claim 7 , wherein the ratio of the gas flow volume(Nm³)/the liquid flow mass (kg) is adjusted to be 10 Nm³/kg or more. 9.A method for manufacturing an aluminum or aluminum alloy sputteringtarget material according to claim 8 , wherein nitrogen gas is used forthe gas flow.